Additive manufacturing (AM) encompasses a variety of technologies for producing components in an additive, layer-wise fashion. In powder bed fusion which is one of the most popular AM technologies, a focused energy beam is used to fuse powder particles together on a layer-wise basis. The energy beam may be either an electron beam or laser. Laser powder bed fusion processes are referred to in the industry by many different names, the most common of which being selective laser sintering (SLS) and selective laser melting (SLM), depending on the nature of the powder fusion process. When the powder to be fused is metal, the terms direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) are commonly used.
Referring to FIG. 1, a laser powder bed fusion system such as system 100 includes a fixed and enclosed build chamber 101. Inside the build chamber 101 is a build plate 102 and an adjacent feed powder reservoir 103 at one end and an excess powder receptacle 104 at the other end. During production, an elevator 105 in the feed powder reservoir 103 lifts a prescribed dose of powder to be spread across a build surface defined by the build plate 102 using a recoater blade 106. Powder overflow is collected in the powder receptacle 104, and optionally treated to sieve out rough particles before re-use.
Selected portions 107 of the powder layer are irradiated in each layer using, for example, laser beam 108, thereby creating a melt pool. After irradiation, the build plate 102 is lowered by a distance equal to one layer thickness in the object 109 being built. A subsequent layer of powder is then coated over the last layer and the process repeated until the object 109 is complete. The laser beam 108 movement is controlled using galvo scanner 110. The selective irradiation is conducted in a manner to build the object 109 in accordance with computer-aided design (CAD) data.
Powder bed technologies have demonstrated the best resolution capabilities of all known metal AM technologies. However, especially with large objects, parameters of the manufacturing process, e.g. the intensity, speed or duration of the irradiation beam, need to be efficiently controlled in order to produce such large objects having multiple parts of varying sizes, geometries or configurations.
In some instances, beyond or alternative to control of the irradiation beam parameters, the temperature of the melt pool in the powder bed may be controlled. For example, US 2017/0051386 (assigned to General Electric Company) describes a manufacturing method where a substrate positioned on a base plate is heated to a predetermined temperature using a first heater, then a melt pool is formed using a laser on a surface of the substrate. A superalloy powder is introduced to the melt pool and the temperature of the melt pool is measured then adjusted accordingly.
However, changing thermal states of the melt pool in the powder bed over the course of a build process can result in thermally-driven deviations of the cross section of the part being built relative to the “baseline” of the built object, i.e., the reference baseline position. If uncompensated, this thermal play between the built object and the apparatus can result in small dimensional errors in size and position relative to what is most desirable.
In view of the foregoing, there remains a need for manufacturing apparatuses and methods that can handle production of objects, especially objects having multiple parts of varying sizes, geometries or configurations, with improved precision and in a manner that is both time- and cost-efficient with a minimal waste of raw materials.